1. Field of the Invention
The present invention relates to a method and apparatus for wafer analysis, and particularly relates to a method and apparatus for analyzing and classifying pattern groups on a wafer according to the distribution of defective patterns.
2. Description of the Related Art
Conventionally, in a semiconductor manufacturing process, a semiconductor wafer is used as a base. Desired components are formed on a single wafer by applying photograph sensitization of photoresistance, metal deposition or evaporation, liquid etching, and other processes.
Generally, patterns are repeatedly formed on a wafer with a plurality of light masks for simplifying the manufacturing process, wherein each pattern is formed independently. A series of etching processes is then achieved, and the wafer is thereafter cut to accomplish a batch of components.
FIG. 1 shows a typical pattern formation on a wafer. On a typical wafer 1, the wafer masks are not repeatedly constructed in the unit of a single pattern mask; instead, the masks are repeatedly formed in the form of masks of pattern groups 3. In a pattern group 3, a plurality of patterns are generally arranged in a matrix, such as the widely used 2xc3x973 matrix as shown in
FIG. 1. In the wafer manufacturing process, the light mask forms a pattern group 3 of 2xc3x973 matrix on a predetermined position with one shot. Thus, with repeated shots, pattern groups 3 are formed on adjacent positions on the wafer.
Occasionally, however, error occur in the above-mentioned manufacturing process, and thus defective patterns may be formed on the wafer. In response to the errors, it is essential to analyze and evaluate the defect distribution on the wafer. If the defective patterns, for example, exist on the right half in nearly most of the pattern groups, it can be interpreted as an error with regularity. In this case, it is possible that errors occurred on the right half of the light mask, or the horizontal alignment of the machine may have been inclined to the right side; other factors that cause regular defective patterns will also be considered. This analysis is the so-called Shot Pattern Recognition (SPR).
Conventional SPR relies on the experience of the operator. That is, no systematic analyzing methods are applied in SPR. In view of this, it is an object of the present invention to disclose a systematic method and apparatus for wafer analysis to address the above-mentioned problem.
The first aspect of the present invention discloses a method for wafer analysis on a wafer with a plurality of pattern groups formed thereon. Each of the pattern groups has a plurality of patterns simultaneously defined by one shot in a development manufacturing process, the patterns of the pattern groups comprising defective patterns failing to comply with a testing condition. The method comprises the steps of: defining a plurality of specific distribution maps, wherein each of the specific distribution maps respectively refers to a defect pattern distribution in a pattern group; defining a plurality of distribution features, wherein each of the specific distribution maps is in relation to one of the distribution features; comparing each of the pattern groups on the wafer to each of the specific distribution maps in order to relate each of the pattern groups to at least one of the specific distribution maps; relating each of the pattern groups on the wafer indirectly to at least one of the distribution features while allocating each of the distribution features indirectly related to each of the pattern groups with a respective relative value according to the relation between the specific distribution maps and the distribution features; and summing up the relative values of each of the distribution features on the wafer respectively to obtain total values of the distribution features.
The method according to the first aspect of the present invention may further comprise a step of: determining the relation between the pattern groups and the specific distribution maps by selecting at least one of the specific distribution maps so that the pattern group correlates to a similar group of characteristics on the selected specific distribution maps.
The method according to the first aspect of the present invention may further comprise a step of: obtaining a reference chart of the total values corresponding to the distribution features.
In the method according to the first aspect of the present invention, the relative values of the distribution features in relation to one of the pattern groups may be respectively set to a value of 1/n where n of the distribution features are in indirect relation to the pattern group, and the number n is a natural number; and the pattern groups may be respectively formed with the patterns in a matrix of axc3x97b, and a and b are both natural numbers.
The second aspect of the present invention discloses a apparatus for wafer analysis for the wafer as described in the first aspect of the present invention. The apparatus comprises a first database for saving a plurality of specific distribution maps, wherein each of the specific distribution maps respectively refers to a defect pattern distribution in a pattern group; a second database for saving a plurality of distribution features; a third database having a plurality of fields, the fields corresponding to the distribution features in the second database; a fourth database for saving the pattern groups on the wafer; a first relating unit for relating each of the specific distribution maps in the first database respectively to one of the distribution features in the second database; a second relating unit for comparing each of the pattern groups in the fourth database to each of the specific distribution maps in the first database in order to relate each of the pattern groups to at least one of the specific distribution maps; an analyzing unit for relating each of the pattern groups in the fourth database indirectly to at least one of the distribution features in the second database while allocating each of the distribution features indirectly related to each of the pattern groups with a respective relative value according to the relations achieved by the first relating unit and the second relating unit; and a computing unit for respectively summing up the relative values of each of the distribution features in the first database to obtain total values of the distribution features, and saving the total values in the fields of the third database.
In the apparatus according to the second aspect of the present invention, the second relating unit may comprise a pattern map comparing unit for determining the relation between the pattern groups in the fourth database and the specific distribution maps in the first database by selecting at least one of the specific distribution maps so that the pattern group correlates to a similar group of characteristics on the selected specific distribution maps.
The apparatus according to the second aspect of the present invention may further comprise an output unit for outputting the total values of the distribution features according to the fields of the third database. The analyzing unit in the apparatus may be provided in a computer, and the output unit may be a computer display, a printer, or a television.
Further, in the apparatus according to the second aspect of the present invention, the relative values of the distribution features in relation to one of the pattern groups may be respectively set to a value of 1/n where n of the distribution features in indirect relation to the pattern group, and the number n is a natural number; and the pattern groups may be respectively formed with the patterns in a matrix of axc3x97b and a and b are both natural numbers.